2014年英语四级考试模拟试题及答案(第三套)_第2页

　　? Sleep is part of a person's daily activity cycle. There are several different stages of sleep, and they too occur in cycles. If you are an average sleeper,

　　your sleep cycle is as follows. When you first drift off into slumber (安睡), y

　　our eyes will roll about a bit, your temperature will drop slightly, your muscles will relax, and your breathing were slow and become quite regular. Your brain waves slow down a bit too, with the alpha rhythm of rather fast waves predominating for the first few minutes. This is called stage 1 sleep. For

　　the next half hour or so, as you relax more and more, you will drift down through stage 2 and stage 3 sleep. The lower your stage of sleep, the slower

　　your brain waves will be. Then about 40 to 60 minutes after you lose consciousness you will have reached the deepest sleep of all. Your brain waves will show the large slow waves that are known as the delta rhythm. This is stage 4 sleep.

　　You do not remain at this deep fourth stage all night long, but instead about 80 minutes after you fall into slumber, your brain activity level will increase again slightly. The delta rhythm will disappear, to be replaced by the

　　activity pattern of brain waves. Your eyes will begin to dart around under your closed eyelids (眼皮) as if you were looking at something occurring in

　　front of you. This period of rapid eye movement lasts for some 8 to 15 minutes

　　and is called REM sleep. It is during REM sleep period, your body will soon relax again, your breathing will grow slow and regular once more, and you will slip gently back from stage 1 to stage 4 sleep — only to rise once again to the surface of near consciousness some 80 minutes later.

　　? 6.The stages of sleep take on ____.

　　? A) an irregular aspect.

　　? B) a regular aspect

　　? C) a punctual aspect

　　? D) a similar aspect

　　? 7.Stage 4 sleep lasts ____.

　　? A) about 80 minutes

　　? B) about 40?60 minutes

　　? C) about 30 munutes

　　? D) about 20?40 minutes

　　? 8.The brain waves are the slowest during ____.

　　? A) stage 1 ?C) stage 4

　　? B) stage 2 and stage 3 ?

　　D) REM sleep

　　? 9.In the second paragraph the word “dart” means ____.

　　? A) glare ?C) stop moving

　　? B) move rapidly or suddenly ?D) gaze

　　? 10.One of the features of REM sleep is that ____.

　　? A) there are large slow waves, though rapid for the first few minutes

　　? B) you have the deepest sleep

　　? C) there are no brain waves

　　? D) the brain waves are a little fast and the brain becomes a little active

　　?Questions 11 to 15 are based on the following passage:?

　　Designing a lens can be compared to playing chess. In chess a player tries

　　to trap his opponent's king in a series of moves. In creating a lens a lens designer attempts to “trap” light by forcing all the rays arising from a single point in the subject to focus on a single point in the image, as a consequence of their passing through a series of transparent( 透明的) elements with precisely curved surfaces. Since in both cases the ultimate goal and the means by which it can be attained are known, one is tempted to think there will be a single best decision at any point along the way. The number of possible consequences flowing from any one decision is so large, however, as to bevirtually, if not actually, infinite. Therefore in lens design, as inchess, perfect solutions to a problem are beyond reach. Although this article will be concerned only with the design of photographic lenses, the same principles apply to all lenses.

　　?

　　The lens designer has one enormous advantage over the chess player: the designer is free to call on any available source of help to guide him through the staggering number of possibilities. Most of that help once came from mathematics and physics, but recently computer technology, information theory,chemistry, industrial engineering and psychophysics have all contributed to making the lens designer's job immeasurably more productive. Some of the lens

　　es on the market today were inconceivable a decade ago. Others whose design is as much as a century old can now be mass?produced at low cost. With the development of automatic production methods, lenses are made by the millions, both out of glass and out of plastics. Today's lenses are better than the best lenses used by the great photographers of the past.Moreover, their price may lower, in spite of the fact that 19th?century craftsmen worked for only a few dollars a week and today's lenses are more complex. The lens designer cannot fail to be grateful for the science and technology that have made his work easier and his creations more widely available, but he is also humbled: it is no longer practical for a fine photographic lens to be designed from beginning to end by a single human mind.

　　? 11.Lens design and chess playing are similar in that ____.

　　? A) the final goal and the means by which it can be reached are known

　　? B) perfect solutions to a problem can be found

　　? C) any one decision at any point along the way to the goal can bring numerous possible results

　　? D) both A and C

　　? 12.The final goal of designing a lens is ____.

　　? A) to trap the opponent's lenses

　　? B) to focus light with lenses

　　? C) to hand?make lenses at low cost

　　? D) to reflect light by means of curved surfaces

　　? 13.After the passage the author will talk about ____.

　　? A) the principles of designing lenses

　　? B) techniques of making contact lenses

　　? C) the design of photographic lenses

　　? D) styles of lenses

　　? 14.Which of the following words cannot be used to describe　today's lenses?

　　? A) More delicate. C) Numerous.

　　? B) Cheaper. D) Unpopular.

　　? 15.Lens designers today ____.

　　? A) have a large source of help to fall back on

　　? B) receive a low salary

　　? C) are less respectable than those of the past

　　? D) are not decisive in the lens design

　　?